1. Field of the Invention
The present invention relates, in general, to a pin connection structure and to a method of connecting members by a pin. Specifically, it also relates to a pin connection structure for use in a floating type brake disc assembly and to a method of connecting the floating type brake disc assembly by pins, the brake disc assembly being for use in a motorcycle.
2. Description of Related Art
As an art of connecting at least two members by a pin, there has been generally practiced to employ a pin connection structure with a hollow pin in order to reduce the weight of the pin. Further, there has also been generally practiced to provide the pin with a surface-treated layer in order to improve the durability of the pin. Specifically, the above-described pin connection structure is also employed in connecting a floating type brake disc assembly by pins.
The applicants of the present invention have been studying how to improve the corrosion resistivity of hollow pins made of various metallic materials such as aluminum alloys, ferrous materials, or the like, by providing them with surface treatment. When an aluminum alloy is used as a material for the hollow pins which are used in a floating type brake disc assembly, the heat generated in the disc due to the friction can be easily transferred to the hub side and, consequently, the heat easily dissipates also from the pins themselves. As a result, the disc can be prevented from being distorted by the friction heat, and also the pins can be made smaller in weight.
However, if an aluminum alloy having applied to the surface thereof a corrosion resistant surface-treated layer such as an oxide coating film (anodic oxidation coating), a chromate film, a metallic coating, a dying coating, a colored coating, or the like, is used under the below-described condition, for making a hollow pin as described below, the surface-treated layer on an end portion of the hollow pin is damaged at the time of caulking, whereby the base surface of the end portion of the pin is exposed to the outside, resulting in a poor-corrosion resistivity and a poor aesthetic appearance. The above-described condition in question is that the shape of a center hole of the hollow pin is formed into the same shape as that of a pin which is designed on condition that it is made in a stainless steel or in a coiled steel material. Such a pin with such a shape is disclosed, for example, in Published Unexamined Japanese Patent Application No. 312700/1996. In more detail, the shape in question is one in which the center hole in the hollow pin is made cylindrical up to the end portion on that side of the pin which is to be caulked, or one in which the end portion of the center hole is chamfered into a linearly tapered shape (i.e., into a shape tapered or beveled in a straight line).
FIGS. 7A and 7B show a construction of a conventional hollow pin as applied to floating type brake disc assembly for use in a motorcycle. The hollow pin is made of an aluminum alloy and which has applied thereto an oxide coating film and in which an end portion of the center hole is provided with a small taper (i.e., a bevel in a straight line). The hollow pin shown in FIG. 7A has a taper a2 in an inner circumferential end portion of the center hole al. This hollow pin “a” is inserted into a connecting hole made of semicircular dents bl, cl formed in a hub b and a disc c, respectively. A washer dl, a coned spring disc e, and a fixing washer d2 are fitted onto an outside of the hollow pin “a” and an end portion of the hollow pin “a” is caulked to thereby radially expand the end portion. The fixing washer d2 is thus fixed in position by caulking. When the end portion is caulked, however, the shape of the end portion changes from the one shown in FIG. 7C to the one shown in FIG. 7D.
At this time, it has been found that a ring-shaped crack f occurs to the oxide film on the end surface, whereby the base surface of the aluminum alloy will be exposed to the outside, resulting in a poor corrosion resistivity and in a poor aesthetic appearance. If the end surface is not tapered, the cracking of the oxide film becomes still larger.
In view of the above points, the present invention has an object of providing a pin connection structure, in general, and a method of connecting, in general, at least two members by a pin.